1. Field of the Invention
This invention relates to a glass roof for closing an opening provided in the roof of a motor vehicle.
2. Description of Related Art
It is known that the roof of a motor vehicle can be at least partially made of a glass pane. Normally, the opening provided in the roof is bordered by a support surface which is used as a stop and which is designed for holding the peripheral edge of the glass pane.
Specifically, the opening generally extends in the transverse direction between the sides of the body, and in the lengthwise direction, between the front roof element which separates the roof from the windshield, and the rear roof element which separates the roof from the back windshield. The side roof elements, the front roof element and the rear roof element each have an individual peripheral stop on the edges facing the opening.
The combination of these four individual peripheral stops forms the support surface for the peripheral edge of the glass pane with a fixed connection which is ordinarily formed by means of cementing.
In practice, a motor vehicle with a glass roof is generally derived simply from a conventional model with a sheet metal roof. This means that the glass pane must be cemented on a normal body, therefore on a non-specific support surface. However, since this support surface, which is used as a stop, is designed to be welded on the base to the sheet metal roof, it does not impose a special requirement for flatness and/or stiffness or continuity.
In the case of cementing the glass pane, this constitutes a major difficulty.
The technique of a fixed connection by means of cementing presupposes a uniform, continuous support surface which runs essentially parallel to the element which is to be permanently connected. In fact, the uniformity and continuity of the adhesive coating are no longer ensured, if there are faults of flatness and/or discontinuities. This results in a major risk with respect to leaks as soon as the glass pane is inserted. If this difficulty is to be eliminated and/or if the distance between the support surface and the surface of the elements which is to be securely joined has overly large irregularities, there can be the tendency to add cement. Unfortunately, in the area of cementing technology, it is known that an excess of cement is not at all compatible with a faultless connection.